1. Field of the Invention
The present invention relates to apparatus providing automated operation of a dump valve for regulating inflation of vehicle suspension pneumatic members.
2. Description of the Prior Art
The present invention provides apparatus for automatically operating a dump valve on a motor vehicle, typically a tractor and trailer combination, having inflated, load bearing pneumatic members. The dump valve deflates and inflates the pneumatic members. Unlike pneumatic members such as gas struts and shock absorbers, the pneumatic members to which the present invention pertains are air filled bladders which serve as shock dampers, pneumatic springs, and as chassis levelers. For purposes of brevity, to distinguish other pneumatic members, and due to descriptive accuracy, these pneumatic members will be termed air bags hereinafter.
In conventional practice, a vehicle is operated with the air bags inflated, since this arrangement properly distributes the load in accordance with axle capacity and braking considerations. To facilitate maneuvering in close quarters, the rearmost axle air bags are deflated, enabling the vehicle to pivot about the remaining axle, and to shorten the wheelbase of the vehicle. This practice is acceptable for low speed maneuvering, but the original condition must be restored for general operation of the vehicle.
It has become general practice to equip such vehicles with switch operated by the driver, which switch opens and closes solenoid operated valve connected to the pneumatic system. Air is vented from the selected air bags when the valve is open, and maintained within the air bags when the valve is closed. When closed, the air supply system of the vehicle will restore initial air pressure.
Systems for automating operation of a dump valve have been proposed, and are exemplified by U.S. Pat. No. 5,052,713, issued to Jeffrey S. Corey et al. on Oct. 1, 1991. Corey et al. employ an electromagnetic proximity sensor to monitor vehicle speed by counting the number of lugs passing thereby in a known time period. Timing means are provided to override the speed input.
Further patents relating to height of a chassis on its suspension include U.S. Pat. No. 2,844,384, issued to George W. Jackson on Jul. 22, 1958; U.S. Pat. No. 2,901,241, issued to Argyle G. Lautzenhiser on Aug. 25, 1959; U.S. Pat. No. 4,555,126, issued to Ikuo Ishimitsu et al. on Nov. 26, 1985; U.S. Pat. No. 4,558,886, issued to Gerald J. Straub on Dec. 17, 1985; German Pat. Document No. 3827807; International Applications published under PCT, International Publication Nos. WO 91/07291 and WO 92/12021; and UK Pat. Document Nos. 869,984 and U.S. Pat. No. 2,237,780. These documents disclose apparatuses and practices common to fluid suspensions, but when taken either singly or in combination, are not seen to describe the instant invention as claimed.